DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 100447
SWODY1
SPC AC 100445

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1145 PM CDT WED MAY 09 2012

VALID 101200Z - 111200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER S TX...

...SYNOPSIS...
A SPLIT FLOW REGIME IN THE MID/UPPER LEVELS WILL PERSIST ACROSS THE
U.S. ON THURSDAY. WITHIN THE NRN STREAM OF THIS REGIME...A SHORTWAVE
TROUGH WILL SHIFT EWD FROM THE NRN ROCKIES TOWARD THE NRN
PLAINS...WHILE A RELATIVELY MORE AMPLIFIED SHORTWAVE TROUGH
DOWNSTREAM MOVES EWD AND REACHES THE EAST COAST BY LATE TONIGHT.
WITHIN THE SRN STREAM...A CLOSED LOW WILL MOVE EWD/ENEWD FROM PARTS
OF NRN MEXICO TO CNTRL TX.

...S TX TODAY INTO TONIGHT...
DCVA/MID-LEVEL HEIGHT FALLS ACCOMPANYING THE AFOREMENTIONED CLOSED
LOW...COMBINED WITH ISENTROPIC ASCENT NORTH OF A WEAK SFC
FRONT...WILL YIELD A THREAT FOR SCATTERED TO NUMEROUS THUNDERSTORMS
THROUGHOUT MUCH OF THE PERIOD. STRENGTHENING MID-LEVEL WLY FLOW IN
ASSOCIATION WITH A SPEED MAX IN THE SRN SEMICIRCLE OF THE CLOSED
LOW...ATOP RELATIVELY BACKED LOW-LEVEL FLOW...WILL SUPPORT
SUFFICIENT DEEP SHEAR FOR ORGANIZED CONVECTION...INCLUDING POSSIBLE
SUPERCELLS. HOWEVER...THERE IS CURRENTLY CONSIDERABLE UNCERTAINTY
REGARDING CONVECTIVE EVOLUTION. ONE OR MORE FORWARD-PROPAGATING
CONVECTIVE COMPLEXES MAY EVOLVE FROM POSSIBLE MORNING CONVECTION
OVER SWRN/S-CNTRL TX...AND/OR FROM ADDITIONAL STORMS DEVELOPING OVER
THE HIGHER TERRAIN OF NRN MEXICO THROUGH THE DAY. DMGG WIND GUSTS
AND SVR HAIL WILL BE THE PRIMARY CONCERNS WITH THIS ACTIVITY...AS IT
ENCOUNTERS RICH LOW-LEVEL MOISTURE AND AT LEAST MODEST ESELY/SELY
INFLOW. THIS THREAT WILL EXTEND TOWARD THE MIDDLE/LOWER TX COAST BY
LATE IN THE PERIOD AS A WEAK SFC WAVE DEVELOPS OVER DEEP SOUTH TX.
THE THREAT FOR A TORNADO OR TWO WILL EXIST...GIVEN VERTICALLY
VEERING WIND PROFILES. HOWEVER...UNCERTAINTY REGARDING OVERALL
CONVECTIVE EVOLUTION/MODE TRANSITIONS PRECLUDES THE INCLUSION OF
HIGHER TORNADO PROBABILITIES AT THIS TIME.

...SERN FL PENINSULA THIS AFTERNOON...
SEA BREEZE BOUNDARIES ARE EXPECTED TO BE ASSOCIATED WITH SUFFICIENT
ASCENT FOR THE DEVELOPMENT OF ISOLATED TO WIDELY SCATTERED
THUNDERSTORMS...PRIOR TO THE ARRIVAL OF MORE SUBSIDENT MID-LEVEL
FLOW TONIGHT. STEEP LOW-LEVEL LAPSE RATES AMIDST SFC DEWPOINTS IN
THE UPPER 60S TO AROUND 70 WILL SUPPORT MODERATE TO POSSIBLY STRONG
INSTABILITY SOUTH OF A FRONT DRAPED ACROSS THE FL PENINSULA.
AND...WITH AROUND 30 KT OF MID-LEVEL FLOW OVER THE SRN PERIPHERY OF
THE ERN U.S. SHORTWAVE TROUGH...DEEP SHEAR MAY BE SUFFICIENT FOR
CONVECTIVE ORGANIZATION WITH AN ISOLATED THREAT FOR DMGG WIND
GUSTS/SVR HAIL.

...NRN PLAINS LATE THIS AFTERNOON INTO THIS EVENING...
LIMITED LOW-LEVEL MOISTURE RETURN AHEAD OF A COLD FRONT ATTENDANT TO
THE SHORTWAVE TROUGH CROSSING THE NRN ROCKIES/NRN PLAINS MAY
CONTRIBUTE TO MARGINAL DESTABILIZATION INVOF THE FRONT. RELATIVELY
HIGHER CHANCES FOR STORMS WILL OCCUR BEHIND THE SFC FRONT LATE THIS
AFTERNOON INTO TONIGHT. HOWEVER...IN THE ABSENCE OF RICHER LOW-LEVEL
MOISTURE...CONVECTIVE INHIBITION FOR SFC-BASED PARCELS ALONG/AHEAD
OF THE FRONT MAY PREVENT THE DEVELOPMENT OF SURFACE-BASED
CONVECTION. SOME CONDITIONAL THREAT FOR STRONG WIND GUSTS CANNOT BE
RULED OUT LATE THIS AFTERNOON INTO THIS EVENING IF SFC-BASED
CONVECTION DEVELOPS...GIVEN STEEP PRE-FRONTAL LOW-LEVEL LAPSE RATES
AND LARGE SFC TEMPERATURE-DEWPOINT SPREADS PER FORECAST SOUNDINGS.
THE RELATIVELY GREATER THREAT FOR THIS OCCURRENCE WOULD BE IN CLOSER
PROXIMITY TO THE STRONGER MID-LEVEL HEIGHT FALLS ACROSS ND.
HOWEVER...CONFIDENCE IN SFC-BASED CONVECTION/ANY SVR POTENTIAL IS
TOO LOW FOR SVR PROBABILITIES AT THIS TIME.

..COHEN/DARROW.. 05/10/2012

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